An Economy of Molecular Dynamics Simulations of Non-equilibrium Phenomena in Physics

A method to reduce the CPU time required for molecular dynamics computer simulations of nonequilibrium phenomena in physics has been developed. At each time step in the simulation of a solid system, a force calculation is performed on only those atoms that satisfy at least one of three criteria: (i) its distance moved, (ii) its acceleration, (iii) its change in acceleration. A fourth criteria on the time interval since the forces on all atoms were updated is also employed. For a gas system, forces of the atoms which fly freely in a certain time interval are not updated until these atoms move in a distance that is greater than a predetermined value. A savings in CPU time greater than a factor of two is obtained with negligible loss in accuracy.